Method for obtaining copper and precious metals from copper-iron sulphide ores or ore concentrates

ABSTRACT

Process for extracting copper and precious metals from copper and iron bearing ores, ore concentrates or minerals, comprising the following steps:
         converting the copper and iron bearing ores, ore concentrates or minerals to copper-containing sulfides and iron sulfides by reaction with sulfur at 300 to 600° C. for at least 5 min;   grinding the reaction product;   physically separating the copper-containing sulfides at least partially from iron sulfides;   treating the separated copper-containing sulfides by pyrometallurgical or hydrometallurgical processes to obtain copper.

The present invention relates to a process for extracting copper from copper/iron-sulfidic ores.

By far the biggest part of the world's copper production (about 90%) is extracted from copper sulfide minerals. Among the copper sulfide minerals, there may be mentioned, above all, chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), cubanite (CuFeS₄), chalcosine (Cu₂S), digenite (CugS₅), covelline (CuS), enargite (Cu₃AsS₄), tennantite (Cu₁₂AS₄S₁₃) and tetrahedrite (Cu₁₂Sb₄S₁₃).

Among the copper sulfide minerals, chalcopyrite is the most widespread mineral; therefore, it is of the greatest scientific and economic importance in the development of new extraction methods.

In addition, chalcopyrite and the above mentioned minerals are characterized by always containing deposited gold, silver, platinum metals and other rare metals as well as rare earths.

The copper-sulfidic and copper/iron-sulfidic minerals are extracted from ores, which are usually milled and concentrated by a flotation process to yield an ore concentrate, whereby a substantial part of the silicates contained in the ground stock, in particular, is separated off.

Today, in addition to the known pyrometallurgical and chemical hydrometallurgical processes, there are various approaches to leaching copper and other metals occurring in the copper sulfide minerals from the ores or ore concentrates using hydrometallurgical bioleaching processes. Like in the hydrometallurgical processes, this involves the problem that only part of the copper contained in chalcopyrite can be leached out using the known processes because passivation of the chalcopyrite occurs, among others, or the leaching times are very long, or there is no continuous leaching, but autoclave processes are applied, which is comparatively uneconomical.

WO 01/44524 describes a process for extracting copper from chalcopyrite-containing ores in which the chalcopyrite-containing ores are converted to covelline, pyrite and accompanying substances by the addition of sulfur and then copper is extracted by leaching steps of the microbiological or chemical type.

Especially for pyrometallurgical processes, but also for hydrometallurgical ones, the plants are designed for a narrow range of the copper to iron ratio.

It was the object of the present invention to develop a process for improving the extraction of copper from copper/iron-sulfidic ores.

This object is achieved by a process comprising the following steps:

Process for extracting copper and precious metals from copper and iron bearing ores, ore concentrates or minerals, comprising the following steps:

-   -   converting the copper and iron bearing ores, ore concentrates or         minerals to copper-containing sulfides and iron sulfides by         reaction with sulfur at 300 to 600° C. for at least 5 min;     -   grinding the reaction product;     -   physically separating the copper-containing sulfides at least         partially from iron sulfides;     -   treating the separated copper-containing sulfides by         pyrometallurgical or hydrometallurgical processes to obtain         copper.

According to the invention, the copper and iron bearing ore, ore concentrate or mineral is converted to copper sulfides, e.g., covelline, and iron sulfides, e.g., pyrite, using sulfur and optionally additives. An iron sulfide core surrounded by copper sulfides is produced thereby.

Then, according to the invention, iron sulfides and copper sulfides are physically separated at least partially at first.

Preferably, at least 70 or 90%, more preferably at least 95%, by weight of the iron sulfides are separated. Then, copper can be extracted from the thus purified copper sulfide using pyrometallurgical and hydrometallurgical processes known to the skilled person, avoiding the problems normally arising from the presence of admixed iron sulfides.

The separation of the copper sulfides and iron sulfides is effected by grinding at first. The copper sulfides are thereby separated from the iron sulfide core. In a preferred embodiment, the grinding process is effected in a rotary kiln or in a fluidized bed reactor in situ by adding grinding balls. In a preferred embodiment, this is followed by said at least partial separation by electrostatic processes, gravimetric processes, magnetic processes, air classification, grain size selection, a hydrocyclone, flotation processes or combinations thereof.

In one embodiment, at least two separation methods are combined.

Another possibility is the selective heating of minerals with microwaves of different frequencies in order to alter the physical properties of individual minerals to enable their being separated off selectively, for example, by magnetic methods.

The ores employed according to the invention typically contain other metal components, especially rare earths, gold, silver, platinum, cobalt, nickel, zinc. Depending on the process control, these can migrate with either the copper sulfide phase or the iron sulfide phase, or be separated off in separate phases.

According to the invention, the precious metals, for example, gold and silver, in the copper-containing phase are preferably enriched almost completely by a diffusion process and thus can also be recovered almost completely among the other copper-sulfidic minerals particularly easily.

Inasmuch as sulfur is obtained in the further processing, it may be advantageously recycled to the starting step of the process.

The copper sulfides obtained can be used in pyrometallurgical or hydrometallurgical copper extraction.

In particular, the pyrometallurgical processing includes a step referred to as “smelting”. In this step, oxygen is blown into the molten material so that the following reactions proceed:

CuS+O₂→Cu+SO₂.

The thus obtained Cu is then typically freed from excess oxygen by adding reducing agents. Subsequently, electrorefining may also be used.

The iron sulfides obtained may be used for preparing iron; it is also possible to use them for adjusting the desired content of iron sulfides in copper extraction by adding iron sulfides, especially in the pyrometallurgical, but also in the hydrometallurgical extraction of copper.

Preferably, the reaction is performed in an inert atmosphere, preferably in a nitrogen atmosphere, but also in argon or in a mixture of the inert gases. Flue gas may also be used, preferably SO₂. In one embodiment, the conversion is performed in a continuous process, preferably in a three-chamber system.

Particularly suitable for the realization is conversion in a rotary kiln or fluidized bed reactor.

Typical reaction times are around 5 min to 24 h, preferably 5 min to 12 h, or 15 min to 24 h, or 0ö.5 h to 24 h, especially from 5 to 90 or from 5 to 60 min.

Temperatures from 300° C. upwards, preferably >400° C., are suitable. The temperature is preferably <500° C., more preferably <475° C., most preferably <450° C. A temperature of from 400 to 450° C. is particularly preferred.

The reaction time is dependent on the grain size of the ores, ore concentrates and minerals employed. Preferred values for d50 are below 210 μm, such grain sizes typically being obtained in the processing of ores by flotation. Grain sizes of d50=410 μm, d50 350 μm and d50=125 μm may also be employed.

The starting materials can be selected from copper-containing ores, ore concentrates or minerals, such as chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), cubanite (CuFeS₄), chalcosine (Cu₂S), digenite (Cu₉S₅), covelline (CuS) and mixtures thereof.

The amount of sulfur employed can be stoichiometric, half-stoichiometric or catalytic.

Depending on the composition of the starting material, the copper-containing sulfides covelline, chalcosine, digenite, bornite or the iron sulfides pyrite or pyrrhotite can be obtained.

The reactions can be described in part by the following equations:

Cu₅FeS₄+3S→5 CuS+FeS₂

Cu₅FeS₄+2S→5 CuS+FeS

CuFeS2+0.5 S→CuS+FeS

EXAMPLES

FIGS. 1 a and b show the conversion of an ore by the converting step employed according to the invention.

FIG. 1 a shows a chalcopyrite-containing ore.

FIG. 1 b shows the converted ore: a pyrite core with a coat of covelline.

FIGS. 2 a and b also show the conversion of an ore by the converting step employed according to the invention. FIG. 2 a: The precious metals silver and gold are uniformly distributed before the treatment with sulfur. FIG. 2 b: Enrichment of the precious metals silver and gold in the copper sulfide after the conversion with sulfur. 

1. A process for extracting copper from copper and iron bearing ores, ore concentrates or minerals, comprising the following steps: converting the copper bearing ores, ore concentrates or minerals to copper-containing sulfides and iron sulfides by reaction with sulfur at 300 to 600° C. for at least 5 min; grinding the reaction product; physically separating the copper-containing sulfides at least partially from iron sulfides; and treating the separated copper-containing sulfides by pyrometallurgical or hydrometallurgical processes to obtain copper.
 2. The process of claim 1, wherein the conversion is performed in an inert atmosphere.
 3. The process claim 1, wherein the conversion is performed in a continuous process.
 4. The process claim 1, wherein the temperature is at 400° C. to 450° C.
 5. The process claim 1, wherein the conversion is performed in a rotary kiln or fluidized bed reactor.
 6. The process claim 1, wherein the grinding process is effected at least partially in a rotary kiln or fluidized bed reactor in situ by adding grinding balls.
 7. The process claim 1, wherein an enrichment of the precious metals in the copper-sulfidic phase takes place during the conversion.
 8. The process of claim 1, wherein the conversion is performed during a period of from 5 min to 24 h.
 9. The process of claim 8, wherein the time is from 5 min to 90 min.
 10. The process of claim 1, wherein the sulfur is added in stoichiometric, half-stoichiometric or catalytic amount.
 11. The process claim 1, wherein the iron sulfides are transferred to a processing step.
 12. The process claim 1, wherein the separation of the copper-containing sulfides and the iron sulfides is effected by electrostatic processes, gravimetric processes, magnetic processes, air classification, grain size selection, hydrocyclone methods, flotation processes or combinations thereof.
 13. The process claim 1, wherein the copper-bearing ores, ore concentrates or minerals are selected from the group consisting of chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), cubanite (CuFeS₄), chalcosine (Cu₂S), digenite (Cu₉S₅) and covelline (CuS).
 14. The process claim 1, wherein the copper-containing sulfides are selected from the group consisting of covelline, chalcosine, digenite, and bornite.
 15. The process claim 1, wherein the iron sulfides are pyrite or pyrrhotite.
 16. The process claim 7, wherein the precious metals contained are recovered from the copper sulfide.
 17. The process of claim 3 wherein the conversion is performed in a three-chamber system.
 18. The process of claim 8 wherein the conversion is performed during a period of from 5 minutes to 12 hours. 